1. Field of the Invention
Embodiments of the invention generally relate to an apparatus and method for removing particles from substrate processing systems.
2. Background of the Related Art
Reliably producing semiconductor device features in the sub-quarter micron and smaller size range is a key technology for the next generation of very large scale integration (VLSI) and ultra large-scale integration (ULSI) of semiconductor devices. However, as the fringes of circuit technology are advanced, shrinking feature dimensions places seemingly insurmountable demands upon conventional processing capabilities. For example, conventional semiconductor processing apparatuses and methods configured to manufacture devices with features larger than a quarter micron are not nearly as sensitive to sub-quarter micron size particle contaminants as newer devices having sub-quarter micron sized features. The smaller features of newer devices make it much easier for a sub-quarter micron sized particle to electrically short features. As a result thereof, conventional clean room technology, processing techniques, and substrate cleaning techniques capable of removing and/or avoiding the generation of particles larger than a quarter micron have been acceptable for conventional device manufacture. However, as the size of features in sub-quarter micron devices continues to decrease, device sensitivity to sub-quarter micron sized particles increases substantially, as a single quarter micron sized particle may electrically short two device features together and render the device defective or inoperable. Therefore, the removal of contaminant particles from semiconductor substrates is a key focus in the manufacture of sub-quarter micron and smaller sized semiconductor features.
In order to maintain acceptable device yields, the semiconductor manufacturing industry has already paid considerable attention to obtaining a high standard of cleanliness during the manufacture of semiconductor devices. Clean room technology in particular has evolved in response to contamination issues, and therefore, particle deposition onto substrates as a result of exposure to clean room environments is generally a minority source of substrate contamination. The majority of substrate contamination generally originates from the process tools, materials, and/or interior walls of the processing chambers themselves. Accordingly, manufacturing techniques often incorporate cleaning processes before, during, and/or after one or more of the substrate manufacturing process steps in order generate substrates having minimal particle contamination thereon. As a result, cleaning processes in conventional semiconductor fabrication lines often account for approximately 30 percent or more of the processing time in the manufacture of a device.
An example of a conventional particle cleaning apparatus and method may be found in U.S. Pat. No. 5,849,135 to Selwyn. Selwyn broadly describes a system for particle contamination removal from semiconductor wafers using a plasma and a mechanical resonance agitator. The method and apparatus of Selwyn forms a radio frequency (RF) driven plasma sheath proximate the surface of the substrate having particle contamination thereon. The substrate surface having the contamination particles thereon is bombarded by positive ions and electrons from the plasma. Additionally, a mechanical resonance vibration device is used to introduce a continual vibration into the substrate in a direction perpendicular to its surface. The combination of the bombardment of the particles by the plasma and the continual mechanical vibration operates to break the bonds between the particles on the substrate surface and the substrate surface itself. Once this bond is broken, the particles move away from the surface of the substrate into the plasma sheath and become negatively charged through contact with the electrons in the plasma. This negative charge operates to attract the particles further into the plasma, and therefore, keeps the particles from redepositing on the substrate surface. Additionally, a flowing gas may be introduced into the plasma in a direction parallel to the surface of the substrate, which may operate to further facilitate moving the dislodged particle away from the substrate surface and out of the plasma itself.
FIG. 1 illustrates a conventional substrate cleaning apparatus having a vacuum chamber 30, which includes an RF electrode 10 and a ground electrode 12. RF electrode 10 is capacitively coupled to an RF power source 18. A retaining ring having clamps 26 thereon is suspended above the substrate 14 to restrict substrate travel. Plasma is formed between the RF electrode 10 and the ground electrode 12 when RF energy is applied to the RF electrode 10 by the RF power source 18. A plasma sheath 22 is located above the substrate 14 and below RF electrode 10. The substrate 14 is caused to vibrate at approximately 10 kHz by means of a conducting post 28 that passes through the walls of vacuum chamber 30 and which is driven by a mechanical vibrator 34. A showerhead 38 is used to introduce a gas into vacuum chamber 30 via an inlet tube, which generally establishes a radial gas flow above the substrate surface. A pair of vacuum pumps 46 permit vacuum chamber 30 to be operated in the 1-10 torr range while the radial gas flow is generated. Strong drag forces generated by the high gas flow rate operate to drive the particulate matter out of the plasma and into the pumping ports of the chamber.
Other conventional apparatuses and methods, use reactive gasses in conjunction with mechanical agitation to remove contamination particles from the surface of a substrate. Reactive gasses are used in an attempt to increase the cleaning efficiency, as conventional cleaning apparatuses not using reactive gases generate a cleaning efficiency that is approximately 70 percent for 1.25 micron size particles. However, even these reactive gas-based cleaning apparatuses fall short of sufficiently removing particles from substrate surfaces for purposes of semiconductor manufacturing, and therefore, there is a need for an apparatus capable of efficiently removing particles from substrates sufficient for use in semiconductor manufacturing processes.